This invention relates to a shock-mounting apparatus designed for supporting a microphone to isolate the microphone from surrounding environmental vibration.
Microphones with vastly improved sensitivity and response characteristics are continually being developed by the audio industry. One such microphone is the dynamic or moving coil type microphone. This microphone has achieved substantial popularity.
A diaphragm and voice coil form a moving component in the dynamic microphone. A permanent magnetic circuit forms a "stationary" component. The diaphgram and voice coil are suspended in the permanent magnetic circuit. Sound waves vibrate the diaphgram. This vibration causes the voice coil to move axially within the "stationary" magnetic circuit. The voice coil movement induces a voltage in the coil. This voltage is the microphone output.
The dynamic microphone is highly sensitive to vibration. Microphones generally and dynamic microphones in particular are most sensitive to axial vibration. This is primarily due to the relatively large mass of the dynamic microphone diaphragm and voice coil. This large mass contributes to the low-frequency acoustical response of the microphone transducer. Unfortunately, the large mass also makes the dynamic microphone sensitive to unwanted, structure-borne, mechanical vibration.
Transmission of structure-borne vibration to the body of the microphone through its supporting structure induces axial movement of the "stationary" magentic circuit. Because of their large mass and resulting inertia, the diaphragm and voice coil tend to remain at rest while the microphone body moves due to vibration. Under these circumstances, the motion of the microphone body relative to the diaphragm and coil generates an unwanted electrical output.
Isolation of dynamic microphones from mechanical vibration is essential to their best use. The microphones may include internal damping mechanisms or external, shock-mounting apparatuses. An advantage of an external shock-mounting apparatus is compatability with various types of microphones, without change of microphone internal structure.
While external shock-mounting apparatuses have been developed and used, one deficiency or another has limited the usefulness of these prior devices. The framework of some external shock-mounting devices produce spurious resonances and secondary vibrations. Other devices are not compliant enough in the axial direction, which is the main direction of dynamic microphone vibration sensitivity.
One popular shock-mounting apparatus completely encircles the microphone to hold it. Because some microphones have on/off switches on the microphone bodies, a mounting device that encircles a microphone body to support it may obstruct microphone on/off switches. Additionally, a mounting device that encircles the microphone requires that the microphone be disconnected from its signal output cable each time the microphone is inserted into or removed from the mounting device. Consequently, a microphone user cannot quickly transfer the microphone from his or her hand to the mounting device, and cannot make the transfer without temporary loss of the microphone output. Also, many microphone models have permanently attached cables precluding their use in a completely encircling mount.